Sparda

Sparda is the demon responsible for defeating Mundus two thousand years ago, and is the father of Dante and Vergil.

Physical Characteristics
In his human form, Sparda looks exactly like his sons. His rebellious nature was that of Dante, while he had the cold personality of Vergil, as stated in the Devil May Cry novels. His hair was swept back and he is always portrayed as wearing a monocle and purple jacket.

In his true form, Sparda was a human sized, humanoid demon, with cloven hooves, a semi-reptilian hide, a pair of sweeping horns, two pairs of insectoid wings and one pair of chiropteran/bat wings. His entire body appears to be made of grey armor with accents and overtones of tyrian purple, and features ornamental decorations, such as gold trimming along his "crown", a vertical red gem in his forehead, as well as gold knee and elbow guards.

The fact that Dante and Arkham also possess these attributes when assuming his visage implies that they are part of his anatomy, rather than armor. An interesting note is that his shadow is in the shape of a demon rather than his human form, suggesting that, unlike his sons Dante and Vergil, his true nature lies in his devil form, which in turn implies that his human appearance is simply a disguise of sorts.

Pre-Games
Sparda was once one of Mundus' loyal demons, but at some point he suffered a change of heart and switched sides, fighting to protect the humans. He defeated Mundus' demon armies, before moving on to the Emperor of Darkness himself. Sparda defeated Mundus, and sent him and his armies back to the demon realm. In order to close the gateway, Sparda used his own blood, along with the blood of a human priestess, in conjunction with his sword and a mystical amulet. He poured his demonic energy into his beloved sword to close the door between realms, the Temen-ni-gru, though this also robbed him of the lion's share of his abilities. As an added measure, he also imprisoned within the tower its gatekeepers, Cerberus, Agni & Rudra, Nevan, Beowulf and Leviathan, and took the names of the Seven Sins in order to imprison them and set them as seals keeping the Temen-ni-gru underground. In Devil May Cry 4 it is revealed that he sealed another path to hell in Fortuna using the Yamato. Sparda's activities over the next two thousand years are shrouded in legend, though it is understood that for a time after defeating Mundus, he ruled over the humans before eventually vanishing. Sparda later appeared in the twentieth century where he met and fell in love with a human woman named Eva, who bore him twin sons.

Devil May Cry 3
Arkham uses the Sons of Sparda to open the gate to the Netherworld, in order to obtain the Force Edge and thus obtaining the powers of Sparda himself. While he is able to use it to temporarily take on Sparda's form, he is unable to truly resonate with it and soon transforms into a hideous demonic blob.

Devil May Cry
Prologue:

"Two milleniums ago, there was a war. Between the human world and the other... the Underworld. But somebody from the Underworld woke up to justice, and stood up against this legion, alone. His name was Sparda. Later, he quietly reigned the human world, and continued to preserve harmony, until his death. He became a legend, The Legendary Dark Knight, Sparda."

Sparda is referenced frequently throughout the game. At the start of the battle with Mundus, Dante finally awakens the true powers of Sparda's sword, and assumes Sparda's form as a new Devil Trigger. In this form, Dante can fly, shoot fireballs from his fists, and summon a spectral dragon. While fighting on the ground during the second part of the boss battle, Dante can also charge the fireballs, and the range of his sword is greatly extended.

Devil May Cry: The Animated Series
It is revealed that Sparda once had two apprentices, the twin brothers Baul & Modeus.

Devil May Cry 4
The Order of the Sword is a group of demon hunters that worship Sparda. Nero, the main protagonist of Devil May Cry 4 is blood linked to Sparda, and referenced multiple times in Sparda's rebellious nature.

The demon Berial implies that he encountered Sparda when he came to the Human World two millennia prior, telling Nero, "You are just like he was..."

Devil May Cry 2
Dante mentions that Sparda once crossed into the Demon world and returned. It is also revealed that Sparda once fought against Argosax and Bolverk.

Powers and Abilities
The exact extent of Sparda's powers remains unknown; but it is shown that his powers surpassed even the "Prince of Darkness" himself. Arkham himself likened obtaining Sparda's power to becoming a god. In Devil May Cry 3, Dante was unable to defeat Arkham, who wielded Sparda sword (and thus Sparda's powers) at the time, until Vergil shows up. However, it should be noted that the Phantom boss in the first Devil May Cry admonished, after being defeated for the final time, that "[Dante's] are definitely the powers of Sparda... No, even more so." . Also, Nero was able to defeat Sanctus, who wielded Sparda and was connected to the powers of The Savior. It is suggested in Devil May Cry 4 that Sparda acquired the true extent of his power by embracing humanity, which would explain why the demons who attempt to augment their own power with Sparda's are unable to defeat the sons of Sparda.

Weapons
Sparda used the Yamato, and also sealed his power into the Sparda (Force Edge) his own trademark weapon. He also used the Luce & Ombra. Although there's no evidence that Sparda used Rebellion before, he gave it to his son, Dante.

Trivia

 * In the Devil May Cry 3 manga, the Seven Sins state that Sparda was once very rebellious, and that Dante's attitude resembles Sparda.
 * In Devil May Cry and Devil May Cry 3, Dante can obtain the "Legendary Dark Knight" costume by clearing Hard mode. In Devil May Cry, this seems to actually be Sparda himself, as Dante's Ebony & Ivory are replaced with Sparda's Luce & Ombra. the sword Yamato is added to his arsenal, but players can still use Alastor. Yamato is basically a clone of Alastor, but when Sparda D.T.s, Yamato turns into the sword Sparda. His Devil Trigger and shadow are that of Sparda's devil form, no matter the equipped Devil Arm, though his abilities still depend on that Devil Arm.
 * In Devil May Cry 3, Dante's "DMC1 Dante" and "Coatless DMC1 Dante" costumes assume the form of Sparda while in Devil Trigger, possibly reference to how Dante, in the end of DMC1, takes the Force Edge and uses Sparda's Devil Form to defeat Mundus.
 * Sparda's coat and general dress being purple appears to be a combination of Vergil and Dante's trademark colors, or rather their red and blue being a split.
 * When Arkham asked Dante what he thought of his father's demon form, Dante replied that it was "like staring into a backed up toilet". This means Dante has a dislike of his father's demon form due to his dislike of his demon heritage by saying: "Father? I don't have a father, I just don't like you, that's all.".